Closed System and Method for Atraumatic, Low Pressure, Continuous Harvesting, Processing, and Grafting of Lipoaspirate

ABSTRACT

A closed system for harvesting fat through liposuction, concentrating the aspirate so obtained, and then re-injecting the concentrated fat into a patient comprises as its main components a low pressure cannula having between about 7 to 12 side holes of about 1-2 mm by 2.0 to 4.0 mm, a spring loaded syringe holder with a helicoidal spring to apply a substantially constant pressure over the full excursion of the plunger, and a preferably flexible collection bag which is also preferably graduated, cylindrical over most of its body and funnel shaped at its bottom, all of which are connected through flexible tubings to a multi-port valve. The multi-port valve has two flutter/duck bill valves which restrict the fluid flow to a one way direction which effectively allows the syringe to be used to pump fat out of a patient and into a collection bag in a continuous manner. After the bags are centrifuged to concentrate the fat, the excess fluids are separated and the valve is re-connected to permit the syringe pump to reverse fluid flow to graft the concentrated fat back into the patient.

CROSS REFERENCE TO RELATED APPLICATION

Priority is claimed to provisional U.S. Patent Application Ser. No.60/828,505 filed Oct. 6, 2006 entitled Method and Apparatus forLipotransfer, the disclosure of which is incorporated herein byreference.

BACKGROUND AND SUMMARY OF THE INVENTION

The autologous grafting of liposuctioned tissue holds much promise inplastic surgery; but being very technique dependent, and lacking asimple apparatus to perform it, it has a reputation for beingimpractical and unreliable. Generally, as presently performed in theprior art, the process requires harvesting with suction cannulasdelicate and finicky adipocytes, separating them, concentrating them,and then re-grafting them a droplet at a time into a three-dimensionalrecipient matrix in aliquots small enough to survive through diffusionyet separated enough to avoid crowding. The process becomes extremelyarduous and time consuming when large volumes are involved. One of theinventors herein has previously invented methods and apparatus forperforming fat grafting as shown in pending U.S. patent application Ser.No. 11/409,294, filed Apr. 21, 2006 and entitled Method and System forPreparing Soft Tissue for Grafting, Enhancing Grafting Results, andGrafting Autologous Fat to Soft Tissue Such as the Breast, thedisclosure of which is incorporated herein by reference. This processand method represents a significant breakthrough and improvement overthe prior are but leaves room for further improvement and refinement.The inventors herein have invented a system comprised of a number ofdevices each of which is novel but which also function together in anovel way to streamline, simplify and implement fat grafting with apractical procedure having a more predictable success.

The process of liposuction, or the harvest of subcutaneous fat, iscommonly performed with a lipoaspirator machine that generates about oneatmosphere vacuum pressure and has a collection flask connected inseries between the suction cannula and the vacuum pump. It is wellaccepted that one atmosphere vacuum pressure is most effective if theintent is to simply remove and discard the fat to reduce excesses inbody contour. However, if the intent is to reinject this aspiratedtissue as a graft, one atmosphere pressure is too high as it inflictssignificant damage to the adipocytes sufficient to render themundesirable for reinjection. Therefore, for the purpose of re-graftingor reinjection it is generally known that lower vacuum pressures, closerto one half an atmosphere should be used to yield better fat graftsurvival. If lower pressures are used however, it reduces the efficiencyof liposuction.

The grafting of lipoaspirated fat is increasingly being recognized as amethod of restoring volume defects and of improving body contourabnormalities such as may be found in the cheeks, the breast or thebuttocks. In addition, tissue carefully harvested by liposuction hasbeen shown to be rich in stem cells capable of regenerating tissue andof improving a number of conditions related to scarring, radiationdamage and even aging. Therefore a method and device that would makethis process of low pressure harvesting, processing and re-injectinglipoaspirated fat simple, practical and reliable would be of greatutility.

The inventors have succeeded in developing such a system that utilizes anumber of novel components uniquely suited to low pressure harvesting oflipoaspirated fat. Each of these components themselves have novel andinventive aspects to them, and together comprise a closed system that isuniquely suited to harvesting fat for reinjection.

The inventors closed system includes as its components a very lowpressure, multiple opening, cannula for aspirating the fat from thepatient; a constant, controlled low pressure syringe mechanism forcontrollably liposuctioning the aspirate out of the patient with minimaldamage to the adipocytes; and a collection bag into which the aspirateis deposited. A multi-port routing valve interconnects these threecomponents with several ports of the routing valve having internal duckbill valves for one way routing of the aspirate both as it is collectedand as it is re-injected. Although reference is made throughout thisdisclosure to a duck bill or flutter valve, it should be understood thatthose terms apply to any design that opens completely and widely, withminimal pressure gradient, which avoids the slit-like openings of othervalve constructions, for example, that force the fat cell suspension tobe damaged as it accelerates through the narrow opening. To performeither of the aspiration or re-injection, the syringe mechanism isrepeatedly operated to in effect “pump” the fluid through the multi-portrouting valve with its one way internal valves. In this way, theaspirate is collected without being exposed to the atmosphere and at lowpressures so as to minimize the damage to the delicate and sensitiveadipocytes. After collection, the bag is disconnected from the routingvalve and one or more bags may be centrifuged at low pressures, such aswith a manual centrifuge, to separate the aspirate within each bag intoits components of serum, concentrated fat and free oil. After beingcentrifuged, the supernatant oil is purged from the top of the bag, theserum fluid is purged from the bottom port, and the concentrated fatremains in the bag for re-injection. To perform re-injection, the bagand cannula are connected to the routing valve at each other's ports asused for aspiration. This connection one-way routes the concentrated fatout of bag into the patient by means of the duck bill valve orientation.Then, after the routing valve and cannula are primed, the very lowpressure syringe is repeatedly operated to withdraw the concentrated fatfrom the bag, and then push it through the routing valve and into thepatient. Alternatively, instead of the spring syringe system, a small1-5 ml syringe is preferably used with a simple spring on the plungerwhich brings it automatically back each time the surgeon's fingers pushdown on it to empty the grafts into the patient. Throughout this processthe aspirate is not exposed to the air, only very low pressures are usedto move the aspirate through the system, a low speed centrifuge is usedto concentrate the fat from the aspirate which can be collected intomultiple bags to speed the concentration process, and the same systemcomponents used to collect the aspirate are used to re-inject theconcentrated fat. This closed system and method provide significantimprovements over the prior art, and will more fully understood byreferring to the drawing figures and description of the preferredembodiment that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a multi-hole cannula suited for very lowpressure harvesting of lipoaspirate;

FIG. 2( a) is a perspective view of a spring activated syringeaspirator;

FIG. 2( b) is an exploded view of the aspirator of FIG. 2( a);

FIG. 2( c) is an exploded view of an alternate design aspirator with twosmaller helicoidal springs;

FIG. 3 is an assembled but transparent view of the syringe aspirator,with a syringe installed therein;

FIG. 4 is a side view of the routing valve, with cutaway detailing thevarious flow paths of aspirate therethrough;

FIG. 5 is a schematic side view detailing the re-arrangement of therouting valve for re-injection of the fat into a patient;

FIG. 6 is a side view of the routing valve detailing its arrangement ofone way valves within it for multi-use such that the same routing valvemay be used for both aspiration and re-injection, depending upon whichof the open side ports is occluded and which is connected to thesyringe;

FIG. 7 is a side view of a lipo-grafting bag partially filled withaspirate separated into its components such as by centrifuging;

FIG. 8 is a perspective of a manual centrifuge particularly useful inon-the-fly centrifuging during a surgical procedure; and

FIG. 9 is a perspective view of the assembled system, having thecannula, routing valve, activated syringe aspirator and lipo-graftingbag all connected in a closed system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As has become known in the art, grafted fat globules have to firstsurvive by diffusion and what is called plasmatic imbibition until theyget revascularized from the recipient bed. Larger globules that have alower surface to volume ratio cannot get enough nutrients to survive andtherefore die off before getting revascularized. This improvedunderstanding of the physiology of graft survival led to the use ofsmaller bore cannulas with smaller openings that harvest smallerglobules of fat. While generally speaking the smaller the better, verysmall is impractical in terms of harvesting efficiency, especially whenlarge volumes are required for the particular procedure. It is wellrecognized today that the ideal harvesting cannulas should havediameters between 2-3 mm and harvesting slits (hole openings) between0.5 and 3 mm.

The most commonly used and commercially available cannulas forliposuction are either blunt ended with a single side hole, three sideholes (Mercedes type) or have an open end protected by a buckethandle-like shield (the Coleman harvesting cannula). While there arealso some cannulas with up to six side holes, they are less popular, andto the inventors' knowledge, never scientifically proven to be superiorto the more commonly used ones. Furthermore, with the standard pressuresused for liposuction, it is commonly believed based on use that too manyholes clog up the preferred small bore cannulas otherwise thought to beuseful for this application.

The inventors are unaware of work in the prior art evidencing thatprogressively increasing the numbers of side holes, while maintainingthe optimal catheter bore of 2.4-2.7 mm and the slit opening of about1.0-2.0 mm by 2.0-4.0 mm can not only improve the efficiency of fatharvesting (volume harvested per to-and-fro stroke of the cannula) butalso achieve excellent harvesting yield at vacuum pressures much lowerthan previously described.

In a study conducted by the inventors, a series of cannulas withincreasing number of side holes (Coleman design, one, two, three and upto nine side holes) were connected to a liposuction aspirator machinethat was progressively dialed down to the gentlest vacuum that wouldstill yield a continuous flow of fat. In three patients the inventorsmeasured at each pressure and with each cannula, the volume oflipoaspirate per 10 strokes in comparable fresh tumesced fields. Theresults confirmed that yield of fat per pass increased linearly with thenumber of side holes in the cannula. Cannulas with 9 holes proved mostefficient at harvesting with pressures as low as 240 mm/Hg. Cannuladiameter was best at 2.4 mm for the skinny patients and 2.7 mm for themore fibrous & obese. This, to the inventors' knowledge, establishes forthe first time that liposuction can be effectively performed withexcellent yield at very low pressures (250-350 mmHg or ⅓ atmospheric)that cause minimal damage to the tissue provided a cannula was used with9-12 side slit like holes measuring about 1.0-2.0 mm by 2.0-4.0 mmdepending upon the bore diameter. With increased bore size, larger holesit is thought could be effectively used to achieve similar results.

As shown in FIG. 1, a cannula 20 comprises a body 22 with a tip 24 whichis inserted within a patient to harvest fat. The body has three seriesof holes 26, each series comprising three holes 26 aligned along thebody length. The other side of the body 22 (not shown) is left intact. Acentral bore 28 may also be provided, as desired.

The inventors postulate that increasing the number of side holes beyond9 and even up to 12 might further improve the process, and have foundsuch results with 12 hole cannulas. However adding too many holes canbecome problematic for two reasons: (a)—structural: more side holesweaken the cannula and there is a real danger that the cannula couldbreak while inside the patient requiring an incision and a scar toretrieve it (a complication that occurred when a poorly designed 12 sidehole cannula was tried; and which would be avoided by the inventorsarrangement of side holes not spread over the entire cross sectionalcircumference of the cannula but instead be limited to about half thecircumference, leaving the other half circumference intact to maintainstructural integrity); (b)—impractical: having too many side holes alongthe shaft of the cannula restricts the excursion range of theliposuction motion as the more proximal holes cause loss of vacuum whenthe cannula is retracted close to the skin insertion site during theback and forth excursions required for liposuction.

The cannula length depends upon the requirements of the patient and theanatomical area to be harvested and the preference of the surgeon. Wemade cannulas for various uses that vary between 15 to 45 cm in length.To avoid breaks and maintain structural integrity the side holes arepreferably aligned along half the circumference, keeping the remaininghalf structurally intact.

Liposuction with the intent to re-inject the harvested tissue iscommonly performed using a syringe and manual pressure generation. Theproblem with this approach is not only cramping and fatigue of theoperator's hand but also inability to effectively control the level ofvacuum achieved. (The hand can generate very high vacuum pressures thatwill destroy a lot of the fat cells, and especially after fatigue andlack of control, the hand often pulls ineffectively with suboptimalpressures). Thus the need for a mechanically activated device that, onceactivated, would pull on the syringe plunger with a constant forcethroughout virtually its entire stroke from completely collapsed inwardto full extension.

While the most simple mechanical design is a spring connected to theplunger, the problem is that commonly available coil springs do not havea flat stress strain curve, especially over the long range of excursionof the syringe plunger that are required for liposuction. We thereforeinvented an apparatus that pulls the plunger of a syringe over itsentire excursion range with the same constant force to generate aconstant controlled low atraumatic negative pressure of about 250-350mmHg. This syringe holder 30 is shown in FIGS. 2 and 3. This apparatusincludes either a set of springs judiciously designed and arranged toprovide a constant force over the entire long range of excursion, or,preferably a specially designed spring construction that uncurls with aconstant force, as shown as item 32 in FIG. 3.

The subject of the invention herein is preferably a device that canactivate a syringe to pull a relatively constant controlled negativepressure over the entire range of its excursion. The inventors haveconceived a number of designs whereby mechanical energy can be storedand then induced to deliver a constant pull force over substantially theentire range of excursion of the plunger. This includes hydraulic or gaspressure activated devices that are either self contained with thehydraulic energy stored within the device or devices that are connectedto a source of hydraulic energy whether a gas tank or a separate pump. Agas tank of the kind generally available in the operating roomsconnected to a pressure regulator device a hose and a mechanicaltransducer to activate the syringe plunger is also a alternative meansof generating a constant vacuum pressure. Alternatively, a batteryoperated electric pump can also be the source of energy that can drivethe syringe plunger with a constant force to generate a constantnegative pressure over its entire range of excursion.

For a purely mechanical (no hydraulic and no electrical) design, thereare a number of alternative means of connecting the syringe plunger tothe spring, including direct connection or indirect with cables andpulleys. The device can be designed to accept standard disposablesyringes and once cocked, can pull on syringe plunger to generate thedesired constant vacuum. Alternatively, instead of the device being anactivator for standard disposable syringes, the device can incorporateits own pistons and cylinders as a stand-alone device that does not needto be loaded with extraneous syringes.

As shown in greater detail in FIGS. 2 and 3, the syringe holder may bemade from molded parts, such as a bottom receiver 34 and cover 36 (shownassembled in FIG. 2( a)). A pair of rings 38 extending from a bracket 40provide a connection point for one or more springs (not shown). Thecustom made syringe device shown in FIG. 3 includes the syringe butt 42encased in a handle 44. A spring casing 46 provides storage for thehelicoidal spring 32, which is preferably used as has been found by theinventors to provide a relatively constant pressure over the course ofits winding and unwinding.

Even if the vacuum pressure of the lipoaspirator machine is dialed downto atraumatic low levels, harvesting the fat with a vacuum source inseries with the collection reservoir has been found by the inventors tobe untenable for many reasons: 1—The collection bottle has to be rigidlest it collapses with the vacuum defeating its function as a reservoir;2—The collection bottle has to remain vertical, lest the harvested fatcontinues its way with the aspirated air flow towards the vacuum pump.This is impractical as it forces the collection reservoir to remain on adedicated stable fixed stand away from the mobile surgical field; 3—thisrequirement adds a few additional feet of tubing with significantopportunity for dead space losses to form; and most importantly,4—adipocytes are well known to be damaged by dessication from highvolume air flow and from air splashes in the collection bottle uponevery instance of vacuum loss (and these tend to be quite frequentwhenever one of the liposuction cannula holes gets close to the skinentrance site).

As an improvement over this prior art, the inventors have developed afat harvesting apparatus whereby the vacuum source and the collectionreservoir are not in series but are rather isolated from each other in aparallel type of configuration. To that effect, the inventors designed arouting valve that isolates the collection reservoir from the vacuumsource and depending upon the applied pressure gradient directs the flowof fat aspirate either towards the vacuum source syringe or towards thecollection bags used for separation and re-injection. Compared to manualliposuction whereby each time a syringe is filled, it has to bedisconnected from the cannula and replaced with an empty one, not onlyis the requirement for syringe supplies reduced but more importantly theoperating time has been found to be reduced by half.

While there are in the market a number of prior art valve based devicesintended to direct the flow of an aspirate or an injectate from areservoir to the recipient source or, acting in reverse from a source toa reservoir, these devices proved not suitable for this applicationwhere the fat is intended to be re-injected. The pressure gradientrequired to reverse flow from opening to closure of the valve ispreferably as close to zero as possible. Hence, all the spring-baseddesigns are not suitable. Furthermore, the flow across the valve has tobe as unrestricted as possible to prevent the damaging highvelocity/high shear flow that a slit like opening from the membranebased valve designs would necessarily impose. Similarly, the rotaryvalves and other ball valves tend to crush the adipocytes as they close.

The inventors have found that the duckbill and the flutter type ofvalves are preferred for this application, for the following reasons.They require very little pressure gradient to open, they open over theentire bore of the tubing, they close gently without snapping to causeminimal damage to the adipocytes, they have no added moving parts, andcan be molded out of biocompatible rubber like material.

Thus, the inventors developed a routing valve consisting of two duckbillor flutter valves positioned in the arrangement presented in FIG. 4 forharvesting and a reversed arrangement shown in FIG. 5 for re-injecting.However, a design modification described in FIG. 6 allows the same valvesetup device to be used for both purposes provided a different fourthopening is plugged or connected to the syringe.

More particularly, as shown in FIG. 4, a three port multi-valve 50 has afirst port 52 for connection with, for example, a Luer lock 54 to asyringe 56, a second port 58 for connection with another Luer lock 60 toa cannula (not shown), and a third port 62 with a Luer lock (64) forconnection to tubing (not shown) for carrying the aspirated fat to acollection bag (not shown). Each of ports 58 and 62 have an associatedpreferably rubber flutter/duck bill valve 66, 68 respectively whichallow one way flow through their associated ports. Preferably, a hardinner sleeve 70 in each valve 66, 68 prevents eversion of theflutter/duck bill valve. As shown in FIG. 5, the valve 50 may beconstructed with the flutter/duck bill valves oriented differently toallow for fat grafting or re-injection. As shown in FIG. 6, a four portmulti-valve 72 may be provided to allow for either aspirating orgrafting, merely be re-connecting the components to different ports.With the set up described above, free oil supernatant accumulationvolume (a measure of adipocyte damage) and percentage graft take were atleast as good as historical controls performed with a manual syringe.With the four port valve as shown in FIG. 6, in harvesting/aspirationmode, the cannula is connected to port D, the syringe to port B, thecollection bag to port C and port A is plugged off. Ininjection/grafting mode, The cannula is connected to port C, the syringeto port A, the collection bag to port D and port B is plugged off.

The tissue aspirated with the cannula, using the syringe driver, isrouted by the valves through sterile tubing to cylindrical candle likecollapsible bags 80 as shown in FIG. 7 with multiple ports at both endsand a bucket handle type or loop 82 at the top. The bag 80 consecutivelyfunctions as: 1—a collection reservoir; 2— a low speed centrifuge tube;3—a concentration device that allows purging out of the separated serumat the bottom, the free oil and accumulated air at the top throughseparate vents/ports 84, 86 respectively; 4—a re-injection bag with aport 88 at the bottom connected through tubing 90 to the routing valvein re-injection mode, and graduations that provide reading of the volumeof concentrated fat grafted.

It is generally accepted that high speed centrifugation destroys thefragile adipocytes and while many surgeons still prefer 3000 rpm @ 1-2minutes centrifugation, there is evidence that even this separation stepwill lead to loss of valuable components from the aspirated tissue suchas stem cells, platelets, and fluid rich in growth factors. Therefore,especially for large volume lipografting many authorities now prefersimple gravity decantation to separate the components of the suctionedfluid. The problem with gravity separation is that it is typically veryslow, and especially should the patient be undergoing surgery. Toaccelerate this process, while avoiding the limitation of a regularcentrifuge, the inventors designed a rotating table top hanger 92 asshown in FIG. 8 for the bags 80. The rotation is done manually and thespeed is around to 100-200 rpm.

All the above individual inventions are organized to work together inharmony. Together, they comprise a closed harvesting, collection,separation, concentration and re-injection system that inflicts minimaldamage to the adipocytes, minimal exposure to air, minimal manipulationof the aspirated material, minimal exchange of syringes and cannulas. Inaddition, it is practical in that it saves time, effort and supplies,which is especially important to achieve better results with less riskof harm to the patient.

Shown together as a complete closed system in FIG. 9, liposuction isperformed with the cannula 100, using the constant pressure device 102,the fat cells are routed by the valves 104 to the collection bag 106where excess aspirated air is vented. The bags 106 are centrifuged bycentrifuge 92 shown in FIG. 8. After centrifugation, the supernatant oilis purged from the upper port and the serum fluid from the bottom portof the bags. The cannula and the constant pressure device arereconnected to the proper ports of the valve, and the bag connected to adifferent port. The concentrated fat is then re-injected through thetubing connecting the bag to the valve working in injection mode.

The inventors describe a novel device that is especially practical forlarge volume adipocyte harvesting and grafting. It is believed that thisinvention reduces operative time and labor while maintaining excellentgraft viability and take. By harvesting at a low constant pressure andkeeping a closed system with minimal exposure to air, minimal transferof the aspirate and manipulation of the fat, the inventors havestreamlined the harvesting, concentrating and grafting steps and madethe procedure practical and reproducible using reduced amounts ofsupplies, effort, and time.

While the inventors have disclosed their invention in the form of theirpreferred embodiments, this disclosure should be understood as merelyillustrative and not limiting in any sense. Various changes andmodifications would be apparent to those of ordinary skill in the artupon reading and learning from the inventors teachings contained herein.Those changes and modifications are fully intended to fall within thescope of the invention which should be limited only by the scope of theclaims appended hereto.

1. A closed system for low pressure harvesting of aspirate from apatient comprising a multi-port liposuction cannula, a constant lowpressure suction device, a repository for receiving the aspirate, and amulti-port valve having a separate port for connection to a separate oneof each of the foregoing whereby activation of the suction deviceharvests aspirate from the patient and through the cannula, through thevalve and into the repository.
 2. The closed system of claim 1 whereinthe cannula has between about seven to about twelve holes, substantiallyall of said holes being each about 1.0 to about 2.0 mm by about 2.0 toabout 4.0 mm.
 3. The closed system of claim 2 wherein said suctiondevice generates about 250 mm Hg to about 350 mm Hg of negative pressureover a controlled period of time.
 4. The closed system of claim 3wherein said cannula has between about nine to twelve holes.
 5. Theclosed system of claim 1 wherein said constant low pressure suctiondevice includes a syringe holder having a spring for attachment to asyringe plunger, said syringe plunger having a matching tube, saidspring being biased to withdraw the syringe from within the tube uponits release.
 6. The closed system of claim 5 wherein said springcomprises at least one helicoidal spring.
 7. The closed system of claim1 wherein said constant low pressure suction device includes a syringedriver.
 8. The closed system of claim 7 wherein said syringe driverincludes a mechanical force applicator for applying a force to thesyringe.
 9. The closed system of claim 8 wherein said mechanical forceapplicator comprises at least one helicoidal spring.
 10. The closedsystem of claim 1 wherein the multi-port valve includes at least threeports, and wherein at least two of said ports have one way internalvalves.
 11. The closed system of claim 10 wherein at least one of saidone way internal valves comprise a duck bill valve.
 12. The closedsystem of claim 10 wherein at least one of said one way internal valvescomprise a flutter valve.
 13. The closed system of claim 10 wherein saidmulti-port valve has four ports, and at least one of said ports may becapped.
 14. The closed system of claim 1 wherein said repositorycomprises a flexible bag having at least one port near its bottom. 15.The closed system of claim 14 wherein said flexible bag is graduated andsubstantially transparent.
 16. A method for harvesting fat throughliposuction with the closed system of claim 1, the method comprisinginserting the cannula into a patient's desired location for removal offat and repeatedly activating the constant low pressure suction device.17. A method for harvesting fat through low pressure liposuctioncomprising inserting a multi-ported cannula into a patient's body, thecannula being connected to a multi-ported valve, operating a constantlow pressure suction device to apply a negative pressure to said cannulathrough said valve, and diverting the flow of fat aspirated through saidcannula through said valve and into a bag for collection.
 18. A closedsystem for continuously aspirating fat from a patient's body, the systemcomprising a negative pressure source, a collection reservoir, a cannulaand a routing valve interconnecting all three so that repeated operationof the negative pressure source generates a continuous flow of aspiratedfat through the cannula, into the valve and on into a collectionreceptacle.
 19. The closed system of claim 18 wherein said negativepressure source comprises a syringe, and wherein said repeated operationof the negative pressure source includes at least partially filling thesyringe and then emptying it in each operation.
 20. The closed system ofclaim 19 further comprising a spring connected to said syringe andbiased to withdraw a syringe plunger from within its receiving tube witha substantially constant pressure.
 21. The closed system of claim 18wherein said routing valve comprises a multi-port valve, and furthercomprising at least two internal one-way valves associated with two ofsaid ports.
 22. The closed system of claim 21 wherein said internal oneway valves comprise either duck bill or flutter valves.
 23. A lowpressure cannula for aspirating fat from a patient's body, the cannulacomprising a cannula body and between about 7 to about 12 holes spacedalong its length, each of said holes being about 1.0 to about 2.0 mm byabout 2.0 to about 4.0 mm each.
 24. The cannula of claim 23 wherein saidcannula body has a bore of about 2.4 to about 2.7 mm.
 25. A multi-portvalve for use in collecting adipocytes during liposuction, the valvehaving at least one internal duck bill or flutter valve associated withat least one port to render that port a one way passage.
 26. Themulti-port valve of claim 25 wherein at least two ports have anassociated internal duck bill or flutter valve, and said internal duckbill or flutter valves are oriented to permit one way flow through bothas fluid enters and leaves the multi-port valve.
 27. The multi-portvalve of claim 25 wherein said multi-port valve includes 4 ports, andwherein at least one of said ports is adapted to be closed to prohibitfluid flow therethrough.
 28. The multi-port valve of claim 27 whereinthe ports having associated duck bill or flutter valves are orientedopposite from another port without a valve.
 29. The multi-port valve ofclaim 28 wherein the multi-port valve has four ports, said four portsbeing situated substantially orthogonally in a common plane.
 30. Aconstant pressure syringe driver device, said device including a bracketfor engaging a syringe plunger and a mechanical force applier attachedto said bracket, said mechanical force applier being biased so that uponits release it withdraws the syringe plunger from within its receivingtube with a constant force.
 31. The syringe driver device of claim 30wherein said mechanical force applier comprises at least one spring. 32.The syringe driver device of claim 31 wherein said spring comprises ahelicoidal spring.
 33. The syringe driver device of claim 30 whereinsaid syringe driver device comprises a holder for receiving a syringe.34. A method for harvesting fat through low pressure liposuction,concentrating the fat, and then re-injecting it with a single closedsystem comprising inserting a multi-ported cannula into a patient'sbody, the cannula being connected to a multi-ported valve, operating aconstant low pressure suction device to apply a negative pressure tosaid cannula through said valve, diverting the flow of fat aspiratedthrough said cannula through said valve and into a bag for collection,centrifuging one or more of said bags to concentrate the fat, separatethe concentrated fat by draining any other fluids from said bags,re-connecting one of said bags to said valve and operating the constantlow pressure suction device to withdraw the concentrated fat from thebag and push it through the cannula back into the patient's body. 35.The method of claim 34 further comprising reversing the cannula andcollection bag connections to said valve after aspirating the fat andbefore re-injecting the concentrated fat.